1. Field of the Invention
The present invention relates to electric connectors and shield devices therefor, which are used to defend against electromagnetic wave disturbance.
2. Description of the Prior Art
Recently, defense against electromagnetic wave disturbance has become necessary for electronic equipment such as a computer etc., and various electric connectors intended to be used to defend circuits from electromagnetic wave disturbance have been disclosed as electric connectors for use in the electronic equipment.
By way of examples, electric connectors are disclosed in the official gazettes of Japanese Patent Application Laying-open Nos. 59-5579 and 59-12583. In these electric connectors, an elastic clip member or earth plate is mounted on a connector housing so as to reliably establish a shield connection with an opposite connector.
Such prior-art electric connectors, however, have the following problems:
(1) Since the clip member or earth plate is constructed so as to lie near the contacts, breakdown voltage and insulation resistance are demeritorious. Moreover, since the clip or plate approaches the contacts, leakage occurs when a radio frequency current flows through the contacts.
(2) Special machining is performed for mounting the clip member or earth plate to a shell, so that the structure of the shell is complicated and the assemblage is accordingly complicated. Therefore, a high price is inevitable.
(3) In a connector disclosed in the official gazette of Japanese Patent Application Laying-open No. 59-12583, an earth plate is mounted on only a part of an insulator housing, and hence, it is impossible to defend the connector from electromagnetic wave disturbance perfectly.
(4) In a connector disclosed in the official gazette of Japanese Patent Application Laying-open No. 59-5579, the spring plate arm of a clip member is fine and is low in mechanical strength. Nevertheless, the contact area of the face of the arm during an inserting or drawing-out (removal) operation is large. Therefore, the repetition of the inserting and drawing-out operations of the connector is liable to cause a drawback such that the arm undergoes permanent strain or damage.
An object of the present invention is to eliminate the disadvantages of the prior-art connectors as described above, and to provide a shield structure for electric connectors which is simple in construction, low in cost and high in touching reliability.